There was public outrage in April as well over a video of a 6-year-old girl getting a pat-down in the New Orleans airport. She was patted down, TSA adminestrator John Pistole said, because she moved during the electronic screening, causing a blurry image.

But this screening has been criticized as being too intrusive and an unnecessary measure for children and older people who seem to pose no terror threat.

Pistole, testifying at a hearing on transportation security by the Senate Homeland Security and Governmental Affairs Committee, said his agency has been working on a new policy for the use of pat-downs on children and an announcement will come soon.

Terrorists in other countries have used children as young as 10 years old as suicide bombers, Pistole said, although that hasn't happened in the U.S. "We need to use common sense," he told lawmakers.

Some of the first information gleaned from Osama bin Laden's compound after he was killed by U.S. forces in May indicated that al-Qaida considered attacking U.S. trains on the upcoming anniversary of the Sept. 11 attacks. Counterterrorism officials have said they believe the planning never got beyond the initial phase and have no recent intelligence pointing to an active plot for such an attack.

But the evidence from bin Laden's compound shows what U.S. officials have been saying for years: Terrorists remain interested in attacking transportation nodes, such as airplanes and trains.